The present invention relates to a prosthetic mounting clip made of biologically absorbable material, used for mounting a prosthetic part in the human body relative to an anatomical support.
According to the present invention, the terms used below in the description and in the claims have the following meanings:
xe2x80x9cbiologically absorbable materialxe2x80x9d is to be understood as meaning a material which is broken down and/or assimilated by and/or in the human or animal body;
xe2x80x9canatomical supportxe2x80x9d is to be understood as meaning nonmineralized human or animal support tissues.
In accordance with FIG. 17 of the document U.S. Pat. No. 5,203,864, a prosthetic mounting clip has been described and proposed in general, having a monolithic structure, made of a biologically absorbable material, comprising:
a distal element or anchoring rod in the anatomical support;
a proximal element or stop bar relative to a prosthetic part;
and a one-piece connecting rod, or strut, linking, on the one hand, the distal anchoring rod, at an intermediate point of the latter, and, on the other hand, the proximal stop bar, at an intermediate point of the latter.
The connecting rod is arranged relative to the distal anchoring rod so as to determine at least two relative or angular positions of said connecting rod, relative to the distal anchoring element, namely:
an inoperative position, corresponding to the initial position (that is to say after producing the clip, for example by molding or injection) of the connecting rod, in which the latter is arranged along a first direction, corresponding to the direction in which the clip is retained, by traction, in the anatomical support;
and a stressed position, with or without elastic return depending on the nature of the biologically absorbable plastic material, in which the connecting rod is folded back along a second direction, against the distal anchoring rod; this second direction corresponds to the direction in which the distal anchoring rod, folded back against the connecting rod, penetrates into and spaces apart the anatomical support in order to anchor the clip in the latter.
Such a clip can be placed in the anatomical support using any device in accordance with that described in the document U.S. Pat. No. 5,203,864 (cf. FIG. 14). This device includes in general a trocar in which a longitudinal continuous slot is formed, cooperating with an internal pusher. The distal anchoring rod of the clip is arranged in the trocar, with the connecting rod passing through the slot. By applying the distal end of the trocar from the outside against the anatomical support and by pushing the internal pusher against the anchoring rod, the latter and the folded-back connecting rod are made to penetrate into the orifice formed by the trocar. Then, when the distal anchoring rod has penetrated into the anatomical support, the trocar is withdrawn.
In accordance with the previously identified prior art, in the inoperative position of the connecting rod (made in one piece), the first direction of the latter is perpendicular to the second direction, also parallel to or coincident with the main direction or plane of the anchoring rod.
Such an arrangement has the disadvantage of applying, at the junction between the connecting rod and the distal anchoring rod, a considerable cumulative angular stress, since equal to 90xc2x0, in order to change from the inoperative position to the folded-back position of the connecting rod, plus 90xc2x0, when the clip is anchored in the anatomical support, in order to return to the inoperative position, under the effect of a traction applied from the proximal stop bar, that is to say 180xc2x0 in total.
As the clip is made of a biologically absorbable plastic material, having mediocre elastic properties, this stress weakens the clip at the abovementioned junction, which often leads to its breaking between the connecting rod and the distal anchoring rod.
The object of the present invention is therefore to remedy this disadvantage. More precisely, the subject of the invention is an arrangement of the clip which limits the cumulative angular stress of the latter at the junction between the connecting rod and the distal anchoring rod.
According to the present invention, in the inoperative position of the connecting rod, at least part of the latter is inclined or oblique relative to the proximal stop bar and to the distal anchoring rod.
By virtue of the invention, for the aforementioned part of the connecting rod, the cumulative angular stress, calculated as before, is at most equal to 135xc2x0, in the case of a 45xc2x0 inclination and a traction completely straightening the connecting rod, perpendicular to the distal anchoring rod.
This solution also brings with it other unexpected advantages.
When the aforementioned part of the connecting rod is straightened, that is to say arranged perpendicular to the distal anchoring rod, its original inclination makes it possible to provide extra anchoring depth, compared to the distance separating the distal anchoring rod and the proximal stop bar, for example parallel to one another. This permits more effective mounting of the clip in the anatomical support.
Nonetheless, the size of the clip in terms of width and height, that is to say the distance separating the anchoring rod and the stop bar, remains limited and remains compatible with the cross section of the tubular conduits used in surgery, in particular in celioscopy or laparoscopy, through which the clip is engaged in the anatomical support. In other words, for the same anchoring depth, the width or height taken up by a clip according to the invention is much less.
According to a preferred embodiment of the invention, a gusset is formed at the junction of the connecting rod with the distal anchoring rod, so that the zone of folding or axis of articulation of the connecting rod against the distal anchoring rod is shifted along the connecting rod, away from the junction zone between the distal anchoring rod and the connecting rod.
This makes it possible to distribute the mechanical bending, extension and traction stresses of the connecting rod relative to the distal anchoring rod about a greater radius of curvature, which fact limits the weakening of the biologically absorbable material at the junction between connecting rod and anchoring rod.
This gusset moreover limits the complete folding-back of the connecting rod on the distal anchoring rod and creates a sufficient interstice between the connecting rod and anchoring rod to promote fastening of the anchoring rod in the anatomical support as soon as the first traction stress arises, and thus promote the return to the inoperative position, and even beyond this if the traction continues.
According to another preferred characteristic of the present invention, the distal anchoring rod includes, at its own distal end, in the direction and in the sense of penetration into the anatomical support, at least one harpoon or redan in the form of a projection, permitting said anatomical support to be spaced apart. This projection, moving away from the distal anchoring rod, extends away from the proximal end of the distal anchoring rod in the direction toward the proximal end of the same rod.
Upon insertion of the clip into the anatomical support, this harpoon or redan makes it possible to transfer the zone of bending stress of the connecting rod from the proximal end of the clip away from the junction between the distal anchoring rod and the connecting rod. The advantage of this is that it causes minimal stressing of this junction zone, which is relatively weak, as has previously been stated.
Preferably in cooperation with the previously described gusset, the zone of bending stress which is situated toward the proximal and rear edge of the harpoon or redan corresponds precisely to the zone or axis of folding back of the connecting rod against the distal anchoring rod.
As regards the biologically absorbable material, the latter is preferably chosen from the group consisting of polymers of p-dioxanone, polyglycolides, polyorthoesters, polymers of trimethylene carbonate, stereocopolymers of L and D lactic acid, homopolymers of L lactic acid, copolymers of lactic acid and a compatible comonomer, such as the alpha-hydroxy acid derivatives. Still more preferably, the biologically absorbable material has a polydispersity of less than 2.